Apparatus for dispensing dry powdered material



Dec. 17, 1963 R. a. DUNAWAY 3,114,482

APPARATUS FOR DISPENSING DRY POWDERED MATERIAL Filed April 30, 1962 2 Sheets-Sheet 1 INVENTOR ATTORN EYJ Dec. 17, 1963 R. H. DUNAWAY 3,114,482

APPARATUS FOR DISPENSING DRY POWDERED MA'I'ERIAL 2 Sheets-sheaf. 2

Filed April 50, 1962 ATTQRN EY S NV TO Ba #22 1% 005 w /y United States Patent 3,114,482 APPARATUS FOR DEPENSING DRY POWDERED MATERIAL, Ralph H. Dunaway, 618 Lafayette Road, Marion Station, Pa. Filed Apr. 30,1962, Ser. No. 191,070

3 Claims. (Cl. 222328) This invention relates to an apparatus for dusting or coating with finely divided powders, and more particularly relates to an apparatus for applying a finely nebulized spray of dusting material to the surface of freshly printed stock in order to dry the wet ink thereon.

It is common practice in the printing and lithographic arts to apply a coating of material to the freshly printed webs so that they will dry more rapidly and thereby prevent impressions of the wet ink on a sheet being stacked from smudging or being smudged by the next successive sheet. This transfer of wet ink from one sheet to another is commonly termed in the trade as offset. While in the past, anti-offset materials have been applied to freshly printed paper from fluid or solvent media, such methods have proven to be unsatisfactory, especially because the.

wet drying materials had a tendency to stain or discolor the unprinted portions. Prior attempts to deposit a cloud from a dry source or media have likewise been for the most part unsuccessful since highly particulate materials build up static charges during handling. These static charges not only make the particles themselves difficult to control, but also the charged particles transfer their charges to the webs or sheets being stacked to-thereby further aggravate an already troublesome condition.

Moreover, the handling of .dry powders is quite sensitive because of variations in atmospheric moisture content, and in high relative humidities the particles are disposed to agglomerate so as to stick to the dispenser as well as to produce undesirable clumps on the freshly printed webs.

Lastly, the fine dry particles have a tendency to cling at random by surface tension to the walls of the reservoir from which they are being dispensed. When a high voltage electrostatic field is juxtaposed to the dispenser in order to free the particles from the surfaces thereof, the material becomes attracted toward the high voltage emitter and frequently builds up on the emitter as a tree. It is not uncommon for the collection to bridge the gap between the emitter and the reservoir. Either ofthe last two mentioned conditions produce in effect a sword of Damocles, for when the build up exceeds the cohesive support, or if the reservoir or emitter is jarred, masses of the agglomerate material would fall as a blob upon the freshly printed stock rather than as a fine mist.

It is therefore an object of this invention toconstruct 7 an apparatus for dispensing dry, highly particulate material in a fine cloud.

Another object of this invention is to provide a fine powder dispenser in whichthe particles will be distributed in a nebulized dust without agglomerating or clinging to the dispenser in unsupported clumps.

Another object of this invention is to provide a fine powder dispenser which will avoid the dissemination of deleterious quantities of dust into the atmosphere.

Another object of this invention is to provide a dry powder dispenser wherein a fine cloud of material may be gently laid upon freshly printed stock and confined within a prescribed limited zone.

Another object of this invention is to construct a dry powder dispenser in which the danger of high voltage electrical shock is eliminated.

Other objects of this invention are to provide an improved device of the character described which is easily See and economically produced, which is sturdy in construction, and which is highly effective and eificientin operation.

With the above and related objects in view, this invention consists of the details of construction and combination of parts as will be more fully understood from the following detailed descriptionwhen read in conjunction with the accompanying drawings in which:

FIG. 1 is a View in vertical section of an apparatus for dispensing dry powdered material'embodying this inven tion, taken along lines 1-1 of FIG. 3.

FIG. 2 is a sectional view taken along lines 2-2 of FIG. 4.

FIG. 3 is a top plan view of the dry powder dispensen FIG. 4 is a front elevational view thereof. Referring now in greater detail to the drawings in which similar reference characters refer'to similar parts, I show an apparatus for dispensing dry, highly particulate material comprising a frame, generally designated as A, a reservoir, generally designated as B, and an electrostatic field producing means, generally designated as C( The frame A may be any suitable supporting means for adjustably elevating the reservoir B above a table top or stock delivery carrier 12. For example, in the embodiment shown, the frame A includes a plurality of posts 14 which are mounted on the table top 12 and a plurality of transverse members 16 secured to the posts and holding the reservoir, as shown in FIG. 1. It is also to be noted that the frame A may be suspended from a ceiling or from an overhanging portion of a machine although not shown in the drawings.

The reservoir B comprises a pair of end plates 20 and 22 held in fixed spaced relationship with each other by side wall members 24 and 26 in substantially rectangular configuration. Since the reservoir B has an open top and essentially an open bottom, a plurality of bolts 28 laterally interconnect the side wall members 24 and 26 intermediate the end plates so as to provide structural rigidity. A cylindrical roller 30 having a shaft 32 is plates.

chaindrive 38. The roller 30 is preferably 2 inch diameter stainless steel, the surface of which is sand blasted and triple chrome plated. While the speed of rotation of the roller 30 may be varied within a range up to 1.78 r.p.1n., I have found a rotational speed of l'r.p.m. to be most satisfactory.

A longitudinally extending wiper blade 40 is secured to the wall 24 by screws 42 and downwardly projects therefrom into resilient tangential engagement with the lower peripheral surface of the roller 30. The blade 49 is stainless steel and has a flange 40a which is originally bent at an angle of 45 from the blade itself. When the flange 40a is mounted to the side wall 24, theblade 40 acts as a fiat spring which the roller 30 flexes away from the side wall 24 at an angle of 32.

A similar stainless steel wiper blade 44, originally bent at 45 from flange 44a, is secured to the side wall 26 by screws 46. The free end of the blade 44 is flexibly urged into tangential engagement with the upper periphery of the roller 30 and is resiliently deformed by the roller surface so as to define an angle of approximately with the wall 26. Both of the blades 40 and 44 respectively overhangthe line of tangency with roller 36 by approximately A; inch. It is easily seen from FIG. 1, that the upper surfaces of the blades in combination with the upper surface of the roller subtended thereby form a container from which'dry, particulate powder St) may be dispensed.

A plurality of spaced bracket plates 52 are secured to the front face of the wall 26 by screws 54, each screw further retaining a pipe clamp 56 for supporting a compressed air tube 58. The tube 58 may be copper tubing or other suitable piping which has a plurality of longitudinally spaced aligned pin holes therein. The pin holes 60 are preferably V inch diameter and spaced one inch apart. One end of the tube 58 is capped, the other end communicating with a supply of compressed air from a tank or compressor (not shown). The air forced out of the holes 60 is adjustably directed downwardly to define a curtain for directionally confining the dispensed powder 50 within a limited zone. See right hand side of FIG. 1. A second compressed air tube 62 with aligned spaced holes is supported within the end plates 20 and 22 for adjustably directing a stream of air downwardly at the left hand side of the roller 39. The air tube 62 is also used to blow out powder accumulating on a catcher pan 64 which is secured to the bottom of wall 24 and laterally extends adjacent the lower periphery of the roller.

The electrostatic field producing means C comprises a dielectric tube 70 within which a conductive tube 72 is loosely supported. The dielectric tube may be any suitable plastic, such as extruded acrylic resin. The conductive tube '72 is preferably brass having an exterior diameter smaller than the inner diameter of the tube '70. One end of the conductive tube 72 is soldered to a cable 74, such as a stranded wire having a jacket of polyethylene and rubber insulation, which is connected to the hot side of a high voltage, A.C., power supply 76 producing a potential of 7,500 to 8,000 volts. The power source 76 is represented symbolically although I prefer to use a Simco Midget Power Pack, model D1682 which has a low current output. It is also to be observed that the conductive tube 72 is fully encapsulated by the dielectric tube 70, end caps 7tla and 76b thereon preventing accidental touching of high voltage by operating personnel. However, the conductive tube '72, while being confined within the interior of tube 70, is not restricted in position therein but is allowed to float loosely. A plurality of dielectric plugs 78 are cemented to the exterior of the tube 70, and have tapped holes therein into which screws 80 are threaded for supporting the static bar C within openings in the brackets 52. Set screws 82 position the screws 78 so that the bar C is adjacent roller 30. As is apparent from the foregoing description, my invention operates in the following manner. Powder 50 is placed in the reservoir B so that it is predisposed to move toward the roller 30 and the blade 40. For purposes of preventing offset, I prefer to use 50 micron cornstarch. With the roller rotating at approximately 1 rpm. in a counterclockwise direction as shown in FIG. 1, the powder 50 will tend to cling in a fine film to the surface of the roller as it passes by the free end of the blade 40 resiliently urged into peripheral contact therewith. A small portion of the powder 50 will fall of its own weight from the roller surface, any agglomerations of the powder dropping upon the catcher pan 64. The electrostatic bar C with the high voltage connected to the tube 72 is adjusted so that the periphery of the tube 70 is approximately /8 inch away from the roller surface. It is to be observed that the roller 30, which is conductive, is

grounded as is the reference side of the electrostatic generator 76. The electrostatic field generated by the emitter bar C wipes the surface of the roller 30 clean of any powder previously adhering thereto, and a clean line of powder demarcation may be noted on the roller immediately adjacent the bar C. None of the powder 5:) is attracted to or clings to the bar C, and as a result, there is no powder build-up or treeing effect occurring. It has been found that the bar C vibrates when the high voltage is applied, and the loose supporting of the conductive tube 72 within the dielectric tube produces a mechanical vibration in addition to the electrostatic field sufficient to prevent any powder accumulations whatsoever on the dielectric tube 79 or its associated brackets.

The powder thus gently falls gravitationally as a fine mist or spray in a dry form upon the paper stock 10. The air streams from the tubes 58 and 62 act as a curtain for the falling powder and maintain the dusting cloud within a generally restricted zone. The air tube 62 is also used to blow out any powder accumulating upon the catcher pan 64 by increasing the air pressure as desired. Since the tubes 58 and 62 are rotatably adjust able, the curtains of air may be oriented over a wide range.

Although this invention has been described in considerable detail, such description is intended as being illustrative rather than limiting since the invention may be variously embodied and the scope of the invention is to be determined as claimed.

What is claimed is:

1. An apparatus for dispensing dry highly particulate material comprising a frame, a conductive cyl ndrical roller journaled in said frame, a substantially fiat blade in said frame longitudinally extending with said roller and resiliently urged into tangential engagement with the lower periphery thereof to define a reservoir for retaining the particulate material, a catcher pan longitudinally positioned below the line of tangency, electrostatic field producing means extending longitudinally with said roller and adjacently spaced from the lower periphery thereof, and means for providing curtains of air directed downwardly from opposing sides of said reservoir whereby said roller during rotation will pick up a film of the particulate material and the electrostatic field will wipe said roller clean so that a cloud of finely dispersed particles may be gravitationally deposited intermediate the curtains of air.

2. The apparatus of claim 1 wherein said electrostatic field producing means comprises a dielectric tube, an electrode loosely supported within the interior of said dielectric tube and fully encased therein, and source of alternating high voltage potential applied across said electrode and said roller.

3. The apparatus of claim 2 wherein said electrode comprises a conductive tube.

References Cited in the file of this patent UNITED STATES PATENTS 1,755,618 Watzl Apr. 22, 1930 2,197,864 Johnson Apr. 23, 1940 2,342,680 Melzcr Feb. 29, 1944 2,737,319 Rayburn Mar. 6, 1956 

1. AN APPARATUS FOR DISPENSING DRY HIGHLY PARTICULATE MATERIAL COMPRISING A FRAME, A CONDUCTIVE CYLINDRICAL ROLLER JOURNALED IN SAID FRAME, A SUBSTANTIALLY FLAT BLADE IN SAID FRAME LONGITUDINALLY EXTENDING WITH SAID ROLLER AND RESILIENTLY URGED INTO TANGENTIAL ENGAGEMENT WITH THE LOWER PERIPHERY THEREOF TO DEFINE A RESERVOIR FOR RETAINING THE PARTICULATE MATERIAL, A CATCHER PAN LONGITUDINALLY POSITIONED BELOW THE LINE OF TANGENCY, ELECTROSTATIC FIELD PRODUCING MEANS EXTENDING LONGITUDINALLY WITH SAID ROLLER AND ADJACENTLY SPACED FROM THE LOWER PERIPHERY THEREOF, AND MEANS FOR PROVIDING CURTAINS OF AIR DIRECTED DOWN- 